1. Field of the Present Invention
The present invention relates to a liquid crystal display unit. More particularly, the present invention relates to a liquid crystal display unit having a quasi-isotropic liquid crystal layer.
2. Description of Related Art
In the development of the display, with the progress in the optoelectronic techniques and the semiconductor manufacturing techniques, the liquid crystal display with the advantages of high definition, optimal space utilization, low power consumption, and no radiation has gradually become the main stream of the market. Currently, liquid crystal materials such as vertically aligned (VA) liquid crystal, twisted nematic (TN) liquid crystal, Cholesteric Liquid Crystal and so on are commonly used in liquid crystal displays. Since optical property and electrical characteristics of different liquid crystal materials are different from each other, various designs of active device array substrate are used to optimize display quality of the liquid crystal displays.
FIG. 1A is a voltage-transmittance (V-T) curve of vertically aligned (VA) liquid crystal. Referring to FIG. 1A, when VA liquid crystal is driven by different voltage, transmittance thereof changes accordingly. Take a liquid crystal display capable of displaying 256 gray levels as an example, the voltage corresponding to transmittance of 100% is defined as driving voltage VL255 corresponding to gray level L255, while the voltage corresponding to transmittance of 0% is defined as driving voltage VL0 corresponding to gray level L0. As shown in FIG. 1A, when the driving voltage VL255 applied to liquid crystal shifts slightly, transmittance of liquid crystal may not change significantly. Accordingly, display quality of the liquid crystal display is stable when the gray level L255 is displayed.
FIG. 1B is a voltage-transmittance (V-T) curve of Kerr effect liquid crystal. Referring to FIG. 1A and FIG. 1B, Kerr effect liquid crystal (e.g. blue phase liquid crystal) and the VA liquid crystal have different optical properties and electrical characteristics. Transmittance of Kerr effect liquid crystal oscillates when the driving voltage increases. Take a liquid crystal display capable of displaying 0-255 gray levels as an example, the voltage corresponding to transmittance of 100% is defined as driving voltage VL255 corresponding to gray level L255, while the voltage corresponding to transmittance of 0% is defined as driving voltage VL0 corresponding to gray level L0. As shown in FIG. 1B, when the driving voltage VL255 applied to liquid crystal shifts slightly, transmittance of liquid crystal changes significantly. Accordingly, display quality of the liquid crystal display is quite unstable when the gray level L255 is displayed.
How to solve the problem of unstable display quality is an important issue of research and development.